"He loved to visit the set and he became famous, like Hitchcock, for appearing in his movies," said the actor, who played Professor X in the X-Men series.

"He created flawed heroes and it was one of the things that made X-Men so interesting for all of us who worked on them," he continued.

"We were always very much aware that no matter what our superpowers were, we were human beings, we could make mistakes and things could go wrong. It was that quality which gave humanity to all of Stan's work."